1. Technical Field of the Invention
The present invention relates to a method for coating a plate with a coating solution containing colorants or ingredients which will afford various functional characteristics such as scratch resistance, antistatic property, antireflection, stain proof, defogging property and light absorbency, so that a coated film with various functional, protective, colored, and design capabilities is formed. A suitable coating apparatus for carrying out the above method is provided as well.
2. Description of the Related Art
As a method for coating chemical solutions to surfaces of a plate, various coating techniques have been conventionally employed, such as dip coating, flow coating, curtain flow coating or roll coating.
However, none of these known methods are fully satisfactory from the viewpoint of productivity or precision of a coated film thickness. For example, a dip coating method allows simultaneous coating to both surfaces of a plate and achieves a high precision of a coated film thickness, but has a disadvantage of very slow coating speed. A curtain flow coating or roll coating method can obtain substantially even coated film thickness at a fast coating speed, but is less productive since a rear side of a plate must be evenly supported, which makes it difficult to coat the both surfaces at a time. Some arrangement can be made for coating both surfaces at a time, but even in this case the production efficiency is not satisfactory since supporting parts are inevitably left uncoated. Further, a flow coating method allows simultaneous coating under a simple operation, but has a disadvantage of inferior precision of a coated film thickness.
In view of the foregoing disadvantage incidental to the prior arts, present inventors studied to develop a productive coating method that provides substantially even thickness of a coated film and allows quick and simultaneous coating to both surfaces of a plate, and an appropriate coating apparatus for carrying out the mentioned method. As a result, a highly productive coating method that af fords desired coating has been established, wherein two coating rolls are placed in such a way that rotation axes thereof are substantially perpendicular to the ground, and the coating rolls are pressed to a plate while the plate passes between the coating rolls.
That is, the present invention provides a method for coating a plate with a coating solution comprising the steps of: holding the plate in such a manner that surfaces of the plate to be coated is aligned in substantially parallel to a gravity direction; moving the plate to a direction parallel to the surfaces of the plate and at right angle to the gravity direction; passing the plate between two coating rolls to which the coating solution is applied, which rotate in contact with the plate to the same direction as that of the plate, and which rotation axes are substantially perpendicular to a moving direction of the plate and to normal direction of the surfaces of the plate; and forming a film of the coating solution on at least one surface of the plate.
In addition, the present invention provides an apparatus for coating a plate with a coating solution comprising: a means for holding and carrying the plate in such a manner that surfaces of the plate to be coated is aligned substantially parallel to a gravity direction, and for moving the plate to a direction parallel to the surface of the plate and at right angle to the gravity direction; two coating rolls placed with such amount of a clearance therebetween that allowing the plate to pass between the coating rolls, which rotate in contact with the surfaces of the plate to the same direction as that of the plate, and which rotation axes are substantially perpendicular to a moving direction of the plate and to normal direction of the surfaces of the plate; and a means for supplying the coating solution to the coating rolls for supplying the coating solution on the surfaces of the coating rolls.